The insulated copper or aluminum wire used in the coils of all types of electromagnetic machines and devices. It is single-strand wire insulated with enamel, varnish, cotton, glass, asbestos, or combinations of these. To meet the immense variety of uses and to gain competitive advantage, a great number of kinds of enamel and of fiber insulations have been developed and are widely available. And to ensure that the many synthetic materials and combinations are properly applied, many elaborate test procedures have been devised to evaluate heat shock, solubility, blister and abrasion resistance, flexibility, and so on as covered in the National Electrical Manufacturers Association (NEMA) Standards. Most important, the thermal endurance is determined by repeated exposure to high temperature, moisture, and electrical stress, as specified in the American Society for Testing and Materials (ASTM).